The effect of pH and redox potential on the redox equilibria of iron oxides in aqueous-based magnetite dispersions was investigated. The ionic activities of each dissolved iron species in equilibrium with magnetite nanoparticles were determined and contoured within the Eh-pH framework of a composite stability diagram. Both standard redox potentials and equilibrium constants for all major iron oxide redox equilibria in magnetite dispersions were found to differ from values reported for noncolloidal systems. The "triple point" position of redox equilibrium among Fe(II) ions, magnetite, and hematite shifted to a higher standard redox potential and an equilibrium constant which was several orders of magnitude higher. The predominant area of magnetite stability was enlarged to cover a wider range of both pH and redox potentials as compared to that of a noncolloidal magnetite system.
Magnetic nanoparticles of Fe₃O₄ were synthesized and characterized using transmission electron microscopy and X-ray diffraction. The Fe₃O₄ nanoparticles were found to have an average diameter of 5.48 ±1.37 nm. An electrochemical biosensor based on immobilized alkaline phosphatase (ALP) and Fe₃O₄ nanoparticles was studied. The amperometric biosensor was based on the reaction of ALP with the substrate ascorbic acid 2-phosphate (AA2P). The incorporation of the Fe₃O₄ nanoparticles together with ALP into a sol gel/chitosan biosensor membrane has led to the enhancement of the biosensor response, with an improved linear response range to the substrate AA2P (5-120 μM) and increased sensitivity. Using the inhibition property of the ALP, the biosensor was applied to the determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The use of Fe₃O₄ nanoparticles gives a two-fold improvement in the sensitivity towards 2,4-D, with a linear response range of 0.5-30 μgL-1. Exposure of the biosensor to other toxicants such as heavy metals demonstrated only slight interference from metals such as Hg2+, Cu2+, Ag2+ and Pb2+. The biosensor was shown to be useful for the determination of the herbicide 2, 4-D because good recovery of 95-100 percent was obtained, even though the analysis was performed in water samples with a complex matrix. Furthermore, the results from the analysis of 2,4-D in water samples using the biosensor correlated well with a HPLC method.
Magnetite (Fe3O4) nanoparticles have been synthesized using the chemical coprecipitation method. The Fe3O4 nanoparticles were likely formed via dissolution-recrystallization process. During the precipitation process, ferrihydrite and Fe(OH)2 particles formed aggregates and followed by the formation of spherical Fe3O4 particles. The synthesized Fe3O4 nanoparticles exhibited superparamagnetic behavior and in single crystal form. The synthesis temperature and the degree of agitation during the precipitation were found to be decisive in controlling the crystallite and particle size of the produced Fe3O4 nanoparticles. Lower temperature and higher degree of agitation were the favorable conditions for producing smaller particle. The magnetic properties (saturation magnetization and coercivity) of the Fe3O4 nanoparticles increased with the particle size.
This paper reports on the preparation of magnetic lumen loaded handsheets from bleached and unbleached mixed tropical hardwood kraft pulps. The lumen coating technique is a physical approach whereby fillers were deposited inside the fibre lumen. In order to produce magnetically responsive fibres, magnetic fillers were loaded into the fibre lumen. The magnetic filler chosen was magnetite which is usually used to make mylar as found in a diskette. Low and high molecular weights of polyacrylamide (PAM) were used as retention aids. The effect of different molecular weight of PAM on filler content in the bleached and unbleached handsheets were studied. The results showed that the amount of fillers deposited in the pulp fibres increased with increasing molecular weight of PAM using both pulps. However the bleached pulps gave better lumen loading than the unbleached when using high molecular weight of PAM.
The mechanical strength of magnetic lumen loaded handsheets was reported to be lower than the unloaded handsheets. This effect is due to the deposition of filler inside the fiber lumen and some on the fibre surface which interfere with the fibre to fibre bonding. Hence, in order to improve the handsheets strength, cationic starch is used as a dry strength additive. In this study, mixed tropical hardwood pulps were used throughout the experiment. The magnetite particles were deposited in the fibre lumen via the lumen loading technique. The addition of cationic starch was found to increase the handsheet strength. However, it disturbed and influenced the location and distribution of the magnetic fillers. Some of the magnetite particles were observed to be displaced from the fiber lumen and pit apertures. The charges of the filler particles and cationic starch played an important role in producing charge repulsion and pulling effect which lead to filler dislocation.
In-situ polymerization method was used to prepare palm-based polyurethane (PU) composites loading with 15 wt% magnetite (Fe3O4), polyaniline (PANI) and Fe3O4 coated with PANI labeled as PU15, PP and PPM, respectively. FTIR spectroscopy analysis indicated a shift in the carbonyl, C=O and NH in PP. The shift of the peak indicated that there was hydrogen bonding between the C=O (proton acceptor) of urethane with NH (proton-donator) of PANI. PPM gave the highest impact and flexural strengths at 4875 kJ/ m2 and 42 MPa, respectively but with the lowest flexural modulus (1050 MPa). Two-stage degradation behavior was observed in the TGA thermogram.
An active heterogeneous Al2O3 modified MgZnO (MgZnAlO) catalyst was prepared and the catalytic activity was investigated for the transesterification of different vegetable oils (refined palm oil, waste cooking palm oil, palm kernel oil and coconut oil) with methanol to produce biodiesel. The catalyst was characterized by using X-ray diffraction, Fourier transform infrared spectra, thermo gravimetric and differential thermal analysis to ascertain its versatility. Effects of important reaction parameters such as methanol to oil molar ratio, catalyst dosage, reaction temperature and reaction time on oil conversion were examined. Within the range of studied variability, the suitable transesterification conditions (methanol/oil ratio 16:1, catalyst loading 3.32 wt.%, reaction time 6h, temperature 182°C), the oil conversion of 98% could be achieved with reference to coconut oil in a single stage. The catalyst can be easily recovered and reused for five cycles without significant deactivation.
Small sized magnetite iron oxide nanoparticles (Fe3O4-NPs) with were successfully synthesized on the surface of rice straw using the quick precipitation method in the absence of any heat treatment. Ferric chloride (FeCl3·6H2O), ferrous chloride (FeCl2·4H2O), sodium hydroxide (NaOH) and urea (CH4N2O) were used as Fe3O4-NPs precursors, reducing agent and stabilizer, respectively. The rice straw fibers were dispersed in deionized water, and then urea was added to the suspension, after that ferric and ferrous chloride were added to this mixture and stirred. After the absorption of iron ions on the surface layer of the fibers, the ions were reduced with NaOH by a quick precipitation method. The reaction was carried out under N2 gas. The mean diameter and standard deviation of metal oxide NPs synthesized in rice straw/Fe3O4 nanocomposites (NCs) were 9.93 ± 2.42 nm. The prepared rice straw/Fe3O4-NCS were characterized using powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDXF) and Fourier transforms infrared spectroscopy (FT‒IR). The rice straw/Fe3O4-NCs prepared by this method have magnetic properties.
The preparation of magnetic nanoparticles coated with chitosan-prindopril erbumine was accomplished and confirmed by X-ray diffraction, TEM, magnetic measurements, thermal analysis and infrared spectroscopic studies. X-ray diffraction and TEM results demonstrated that the magnetic nanoparticles were pure iron oxide phase, having a spherical shape with a mean diameter of 6 nm, compared to 15 nm after coating with chitosan-prindopril erbumine (FCPE). Fourier transform infrared spectroscopy study shows that the coating of iron oxide nanoparticles takes place due to the presence of some bands that were emerging after the coating process, which belong to the prindopril erbumine (PE). The thermal stability of the PE in an FCPE nanocomposite was remarkably enhanced. The release study showed that around 89% of PE could be released within about 93 hours by a phosphate buffer solution at pH 7.4, which was found to be of sustained manner governed by first order kinetic. Compared to the control (untreated), cell viability study in 3T3 cells at 72 h post exposure to both the nanoparticles and the pure drug was found to be sustained above 80% using different doses.
Although nanoparticle-enhanced biosensors have been extensively researched, few studies have systematically characterized the roles of nanoparticles in enhancing biosensor functionality. This paper describes a successful new method in which DNA binds directly to iron oxide nanoparticles for use in an optical biosensor. A wide variety of nanoparticles with different properties have found broad application in biosensors because their small physical size presents unique chemical, physical, and electronic properties that are different from those of bulk materials. Of all nanoparticles, magnetic nanoparticles are proving to be a versatile tool, an excellent case in point being in DNA bioassays, where magnetic nanoparticles are often used for optimization of the hybridization and separation of target DNA. A critical step in the successful construction of a DNA biosensor is the efficient attachment of biomolecules to the surface of magnetic nanoparticles. To date, most methods of synthesizing these nanoparticles have led to the formation of hydrophobic particles that require additional surface modifications. As a result, the surface to volume ratio decreases and nonspecific bindings may occur so that the sensitivity and efficiency of the device deteriorates. A new method of large-scale synthesis of iron oxide (Fe3O4) nanoparticles which results in the magnetite particles being in aqueous phase, was employed in this study. Small modifications were applied to design an optical DNA nanosensor based on sandwich hybridization. Characterization of the synthesized particles was carried out using a variety of techniques and CdSe/ZnS core-shell quantum dots were used as the reporter markers in a spectrofluorophotometer. We showed conclusively that DNA binds to the surface of ironoxide nanoparticles without further surface modifications and that these magnetic nanoparticles can be efficiently utilized as biomolecule carriers in biosensing devices.
Graphene oxide-iron oxide (GO-Fe3O4) nanocomposites were synthesised by co-precipitating iron salts onto GO sheets in basic solution. The results showed that formation of two distinct structures was dependent upon the GO loading. The first structure corresponds to a low GO loading up to 10 wt%, associated with the beneficial intercalation of GO within Fe3O4 nanoparticles and resulting in higher surface area up to 409 m(2) g(-1). High GO loading beyond 10 wt% led to the aggregation of Fe3O4 nanoparticles and the undesirable stacking of GO sheets. The presence of strong interfacial interactions (Fe-O-C bonds) between both components at low GO loading lead to 20% higher degradation of Acid Orange 7 than the Fe3O4 nanoparticles in heterogeneous Fenton-like reaction. This behaviour was attributed to synergistic structural and functional effect of the combined GO and Fe3O4 nanoparticles.
This study investigated heat transfer in magnetohydrodynamic (MHD) mixed convection flow of ferrofluid along a vertical channel. The channel with non-uniform wall temperatures was taken in a vertical direction with transverse magnetic field. Water with nanoparticles of magnetite (Fe3O4) was selected as a conventional base fluid. In addition, non-magnetic (Al2O3) aluminium oxide nanoparticles were also used. Comparison between magnetic and magnetite nanoparticles were also conducted. Fluid motion was originated due to buoyancy force together with applied pressure gradient. The problem was modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions were obtained for velocity and temperature. Graphical results were plotted and discussed. It was found that temperature and velocity of ferrofluids depend strongly on viscosity and thermal conductivity together with magnetic field. The results of the present study when compared concurred with published work.
Triethoxyphenylsilane (TEPS)-functionalized magnetic palm-based powdered activated carbon (MPPAC-TEPS) was prepared and characterized using various spectroscopic methods, and then tested for the removal of bisphenol A, carbamazepine, ibuprofen and clofibric acid. Magnetite film on MPPAC-TEPS was homogeneously coated on the outer surface of palm-based powdered activated carbon (PPAC) through a hydrothermal co-precipitation technique. Followed by silanization of phenyl-functionalized organosilane on MPPAC's magnetic film. As results, micro/mesopore surface area and volume increased without significant pore clogging and iron (Fe) dissolution under the acidic conditions was greatly decreased. The unique structural and chemical features of MPPAC-TEPS were found to be the main reasons for the enhanced adsorption rates and removal capacities of POPs. The presence of electrolytes and different pH values greatly affected the sorption efficiencies. The dominant sorption mechanism of POPs by MPPAC-TEPS was determined to be π-π interaction (physisorption), based on thermodynamic (ΔG°) and differential scanning calorimetry (DSC). Thermal regeneration at a low temperature (350 °C) was an effective method to desorb the retained POPs and enabled to reactivate MPPAC-TEPS with sustained sorption rates and capacities, whereas PPAC was largely exhausted. As a new type of sorbent for POPs, MPPAC-TEPS has operational advantages, such as magnetic separation and stable regeneration.
Clean water is very important for health and well-being of humans and ecosystem. However, over the year, a billion tons of industrial waste, fertilizers and chemical waste were dumped untreated into water bodies, such as rivers, lake and oceans contributing towards water pollution, then threatening human health and ecosystem. Hence, the need for clean water has urged scientists to research and find solutions for improving water quality. Application of nanoparticles in wastewater treatment improves the environmental quality by elimination of harmful pollutants in wastewater. Magnetite is one of the nanoparticles used in wastewater treatment because of its specific large surface area, high reactivity in adsorption and recoverable from treated water via magnetic separation technology. Preparation method of magnetite nanoparticles is the important key to its adsorption efficiency.
A new facile magnetic micro-solid-phase extraction coupled to gas chromatography and mass spectrometry detection was developed for the extraction and determination of selected antidepressant drugs in biological fluids using magnetite-MCM-41 as adsorbent. The synthesized sorbent was characterized by several spectroscopic techniques. The maximum extraction efficiency for extraction of 500 μg/L antidepressant drugs from aqueous solution was obtained with 15 mg of magnetite-MCM-41 at pH 12. The analyte was desorbed using 100 μL of acetonitrile prior to gas chromatography determination. This method was rapid in which the adsorption procedure was completed in 60 s. Under the optimized conditions using 15 mL of antidepressant drugs sample, the calibration curve showed good linearity in the range of 0.05-500 μg/L (r2 = 0.996-0.999). Good limits of detection (0.008-0.010 μg/L) were obtained for the analytes with good relative standard deviations of <8.0% (n = 5) for the determination of 0.1, 5.0, and 500.0 μg/L of antidepressant drugs. This method was successfully applied to the determination of amitriptyline and chlorpromazine in plasma and urine samples. The recoveries of spiked plasma and urine samples were in the range of 86.1-115.4%. Results indicate that magnetite micro-solid-phase extraction with gas chromatography and mass spectrometry is a convenient, fast, and economical method for the extraction and determination of amitriptyline and chlorpromazine in biological samples.
Polypyrrole-magnetite dispersive micro-solid-phase extraction method combined with ultraviolet-visible spectrophotometry was developed for the determination of selected cationic dyes in textile wastewater. Polypyrrole-magnetite was used as adsorbent due to its thermal stability, magnetic properties, and ability to adsorb Rhodamine 6G and crystal violet. Dispersive micro-solid-phase extraction parameters were optimized, including sample pH, adsorbent amount, extraction time, and desorption solvent. The optimum polypyrrole-magnetite dispersive micro-solid phase-extraction conditions were sample pH 8, 60 mg polypyrrole-magnetite adsorbent, 5 min of extraction time, and acetonitrile as the desorption solvent. Under the optimized conditions, the polypyrrole-magnetite dispersive micro-solid-phase extraction with ultraviolet-visible method showed good linearity in the range of 0.05-7 mg/L (R2 > 0.9980). The method also showed a good limit of detection for the dyes (0.05 mg/L) and good analyte recoveries (97.4-111.3%) with relative standard deviations
Nanoparticles of undoped and copper doped with Fe3
O4 of three concentrations (0.5, 1.0 and 1.5) are synthesized by
sonochemical method. Structural, optical and morphological properties of these compounds were studied. Fe2+/Fe3+
ratio is found to be 2.36. Crystalline structure, lattice parameters, surface morphologies, direct and indirect band gap
energies of the synthesized compounds were estimated and the results are discussed in detail. The XDR analysis indicates
the Cu doped Fe3
O4
nanoparticles have higher crystallinity than undoped samples. Average crystallite size is found
to increase as Cu concentration increased. The FTIR results are proven by the presence of mixed magnetite-hematite
nanostructures and it is complement to the XRD results. The presence of spherical, polygonal and agglomeration forms
of the particles are visually seen in the SEM images. Direct and indirect band gap energy is found to be decreased as the
copper concentration was increased.
There are a large number of primary structural planes of deep rock ore such as rhyolite, and bedding, which are well preserved and are often the geological interfaces of mineralization. Study on the occurrence of these structural planes is helpful to understand the extension direction of deep veins. Using borehole imaging technology as the means of acquiring information of structural plane, the magnetic angle of the borehole is obtained by using the gyroscope and the magnetic instrument and the structural plane occurrence is modified to obtain the accurate information. According to the depth effect of the deep structural plane, the concept of the feature point pair is proposed. In this paper, the mathematical description method of the structural plane in the space coordinate system is established and the information of the shape and depth of the structure plane is transformed into the 3D point coordinates in the space coordinate system. Based on the feature points, the connectivity analysis method of structural plane is established and the connectivity of the structural planes such as the interface of the vein and rhyolite is analyzed. According to the stratigraphic information in the borehole image, the extension direction of the whole field is determined. The feasibility of the method is verified by the application in a magnetite in Anhui Province, China. The results are in good agreement with the actual drilling results and the error of traditional drilling analysis is corrected. The main conclusions of this paper include: The use of gyroscopes and magnetic instrument can obtain the magnetic effect angle, to modify the structural plane information; and multi borehole structural planes connectivity analysis can provide a reference for the extension of the deep veins.
Lung cancer, breast cancer and colorectal cancer are the most prevalent fatal types of cancers globally. Gallic acid (3,4,5-trihydroxybenzoic acid) is a bioactive compound found in plants and foods, such as white tea, witch hazel and it has been reported to possess anticancer, antioxidant and anti-inflammatory properties. In this study we have redesigned our previously reported anticancer nanocomposite formulation with improved drug loading based on iron oxide magnetite nanoparticles coated with polyethylene glycol and loaded with anticancer drug gallic acid (Fe₃O₄-PEG-GA). The in vitro release profile and percentage drug loading were found to be better than our previously reported formulation. The anticancer activity of pure gallic acid (GA), empty carrier (Fe₃O₄-PEG) nanocarrier and of anticancer nanocomposite (Fe₃O₄-PEG-GA) were screened against human lung cancer cells (A549), human breast cancer cells (MCF-7), human colon cancer cells (HT-29) and normal fibroblast cells (3T3) after incubation of 24, 48 and 72 h using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) MTT assay. The designed formulation (Fe₃O₄-PEG-GA) showed better anticancer activity than free gallic acid (GA). The results of the in vitro studies are highly encouraging to conduct the in vivo studies.